Bad fuel rail pressure sensor

Tiny
JACOB LAST
  • MEMBER
  • 2005 FORD FOCUS
  • 2WD
  • AUTOMATIC
  • 112,000 MILES
The ECU in my wagon is throwing the P0193 - Fuel Rail Pressure Sensor High fault code. I have an OBDII bluetooth reader and have reset the ECU fault codes and have been monitoring the reading from the FRP sensor while driving. It gives a nice flat reading of 40 psi most of the time but once in a while (especially when the car first starts) pegs out to the maximum 5V reading of 72 psi. When this happens it is almost always while I am coasting or idle, then usually goes back to a normal reading when I accelerate again. I do not notice any difference in the engine when the sensor pegs to 72 psi. It can go quite a while (a week or so) without an errant FRP sensor reading, but then it will peg out again briefly and throw a P0193 code again. This seems to me like a bad sensor, am I right? Is there any other explanation (intermittently failing fuel pump, for instance) that might be the cause of this? I am getting ready to order a replacement sensor and wanted to run this by someone knowledgeable first. Thank you!
Monday, July 18th, 2016 AT 6:35 AM

3 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
As you have checked fuel pressure that may be the problem with it going over 70 psi. But try the sensor first then if it continues you might try a fuel pressure regulator. It cold be a PCM problem however as well.
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Monday, July 18th, 2016 AT 7:06 AM
Tiny
JACOB LAST
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  • 2 POSTS
Thanks, I do not have a gauge so I have not checked the fuel pressure at the fuel rail (I assume that is what you are saying). One thing I forgot to mention: when the sensor goes up to the max reading of 72 psi, it is a perfectly flat line on the graph which does not look like a real sensor reading, as opposed to when it is giving a normal reading at 42psi, which is a bumpy line that looks like the real pressure variation as the PCM ramps the duty cycle of the fuel pump to maintain a steady pressure at the injectors.
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Monday, July 18th, 2016 AT 8:12 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Well you can rent a gauge instead of the way you took it auto parts rent it. But I would replace the sensor electrically is the best way to test fuel pressure.
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Monday, July 18th, 2016 AT 9:27 AM

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